Process for vulcanizing rubber



r Patented-D 27, 1921.

UNITED STATES WI LIS A. means, or LITTLE PATENT OFFICE.

nnox, NEW roux, ASSIGNOB 'ro 'rnnnanen rucx onnmzrca'r. com'rm, or NAUGATUCK, CONNECTICUT, A conrpnnmou :1! concombined with the latex.

Where latex is to be employed after the lapse of considerable time from collection it i as " sumers who em 10 processes ordinarily including its coagulationis usually customary to add up to 3% of an alkali material such as ammonia or a mutity of some other preservative suc as formaldehyde inorder to stabilize it and preserve it inuncoagulate'd condition. In this condition 'it usually appears in. those markets Which are remote from the rubber plantations and is there purchased .by conit-in manufacturing or'desiccation with subsequent vulcanization. It is not practicable to employ all of the vulcanizing agents and ingredients ordinarily used with crude rubber, for addition to such alkali-treated-latex, since ammonia and similar alkali tend to decompose some out these materials with consequent loss in their vulcanizing power. Also some vi11- canizing ingredients tend to cause coagulation of the latex. I

The principal object of the present invention accordingly is to provide a simple, efficient process for preparing a stable latex composition for vulcanization comprising a vulcanizing accelerator.

The invention accordingly comprises a process for preparing, dryin and vulcanizmg a latex composition whic includes combining'with latex,-containing an alkali preservat1ve,a hi h-powered organic accelerator, stable towar does not coagulate thelatex. It also includes products of such process. l

The expression high powered or anic accelerator as used herein Bis intends to designate an organic accelerator which when employed with rubber 'for acceleration of vulcanization is able to" accomplish satisfactory vulcanization in a'relat vely short time or at relatively low temperatures or both. For example 2 parts or less of a high powered accelerator when mixed with v100 parts of pale crepe rubber, 10: arts of zinc oxide, 3 parts of sulphur an vulcanized the. preservative and which raoonss non vntcamzmo RUBBER.

Application sled December 17, 1923. Serial No. 681,079.

under 4.0 lbs. steam presure for minutes will yield a vulcanizate having a tensile stringth greater than 2000 lbs. per square inc i In'carrying out the invention in its p r'eferred form 100 parts 'of-rubber (employed in the form of latex containing 2% ammonia and having. approximately 35% solid content) is combined with 1 part of zinc dimethyldithiocarbaniate- 4 s)2 2)2 1 part of zinc oxide and 3 arts of precipitated sulphur. The zinc dimet yldithiocarbamate, zinc oxide and sulphur are mixed'to a thin paste with dilute ammonium hydroxide.

The paste is then added slowl stant stirring of the latex.

with conpon drying and heating the resulting composition to 212 F. for 40 minutes vulcanization is accomplished. The stability of the composition formed as above is influenced by the quantity of zinc oxide present. The lower the amount of zinc oxide the less the tendency to coagulate. Instead of em laying latex containing 35% solid materia higher and lower concentrations have been satisfactorily employed. Instead of, desiccation of the composition, coagulation may be carried out and in case the coagulant used such as acetic acid dissolves the zinc oxide or other ingredient ordinarily more of this'ingredient is preferably employed in the composition, or zinc acetate may be employed.

Ewample 2.-100 parts oi rubber. (em

ployed in the form of latex containing 9% ammonia and havin approximately 35% solid content) 'is com ined with 1 partoftetramethylthiuramdisulphide, 2 parts of zinc oxide and 3 arts of sulphur. The tetramethylthiuram isulphide, zinc oxide and sulphur are mixed to form a paste with dilute ammonium hydroxide and added as before to the latex. Upon drying and heat- .ing the resulting composition to 212 F. for

40 minutes vulcanization is accomplished. It appears that the vulcanizing ingredients react while-in the latex, the resulting composition consisting of latex, zinc dimethyldithiocarbainate, zinc? oxide and sulphur.

inc

- mixture may be sprayed to give a smooth film to serve as a protective and decorative coating for example on wood, metal and other materials. Upon being maintained for 14 hrs. at 265 F. a hard film is obtained which resists the action of acids other than strong nitric and sulphuric acid and of organic solvents.

Example 4.The following composition is prepared: 100 parts of rubber (employed in the form of latex containing 2% ammonia and having approximately solid content), is combined with 1 part of tetramethylthiuraminonosulphide, 2 parts of zinc oxide and 3 parts of sulphur. The tetramethylthiurammonosulphide, zinc oxide and sulphur are mixed to form a paste with dilute ammonium hydroxide'and added as before .to the latex. Upon drying and heating the s resulting composition to 212 F. for 40 *minutesvulcanization is accomplished. It

appears that the vulcanizing ingredients react while in the latex, the resulting composition' consisting of latex, zinc dimethyldithiocarbamate, zinc oxide and sulphur. The remarks made concerning the stability and coagulation given in Example 1 also apply to the composition of the present example.

The materials zinc dimethyldithiocarbamate, tetramethylthiuramdisulphide and tetramethylthiurammonosulphide are representatives of three classes of high-powered salt forming element or group such as zinc,

ammonium, etc. or hydrogen or a radical SCR or OR.

Compositions formed v in accordance with the above examples are relatively stable. They may be employed for treatment of cords, for the preparation of weftless fabric and for other treatments of fibrous materials. They ma be employed for dipping, modeling, mol ing,'etc.

It will be observed in accordance with the examples that the time and temperature employed for vulcanization is about the same as that ordinarily employed when crude rubber is used showing that the presence of ammonia has been substantially without deleterious effect on the vulcanizing action of the resulting composition. Furthermore, the vulcanizing ingredients do not cause the latex to coagulate.

As many apparently widely different embodiments of this invention may be made without departing from the spirit thereof itwill be understood that I do not intend to limit myself to the specific embodiments 

